U.S. patent application number 12/379538 was filed with the patent office on 2009-11-19 for camera.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Satoshi Ejima, Hirotake Nozaki, Akira Ohmura.
Application Number | 20090284645 12/379538 |
Document ID | / |
Family ID | 39156949 |
Filed Date | 2009-11-19 |
United States Patent
Application |
20090284645 |
Kind Code |
A1 |
Nozaki; Hirotake ; et
al. |
November 19, 2009 |
Camera
Abstract
A face detecting section of a camera detects a face area in a
shooting screen under an output of an image sensor. A focus
detecting section calculates a defocus amount from a relative
interval of a pair of images under an optical flux passed through a
shooting lens in each of optional areas in the shooting screen. A
first focus controlling section specifies a focus detecting area
from the optional areas under an output of the face detecting
section, and performs a focus operation under the defocus amount of
the focus detecting area. A second focus controlling section
calculates a focus evaluation value in the face area under an
output of the image sensor, and performs a focus operation by using
the focus evaluation value. A control section causes at least one
of the first focus controlling section and the second focus
controlling section to perform a focus operation.
Inventors: |
Nozaki; Hirotake; (Port
Washington, NY) ; Ejima; Satoshi; (Tokyo, JP)
; Ohmura; Akira; (Tokyo, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
NIKON CORPORATION
TOKYO
JP
|
Family ID: |
39156949 |
Appl. No.: |
12/379538 |
Filed: |
February 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2007/000921 |
Aug 28, 2007 |
|
|
|
12379538 |
|
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Current U.S.
Class: |
348/349 ;
348/E5.045; 382/195 |
Current CPC
Class: |
H04N 5/232123 20180801;
H04N 2101/00 20130101; H04N 5/23212 20130101; H04N 5/232122
20180801; G02B 7/36 20130101; H04N 5/23218 20180801; H04N 5/23219
20130101; G03B 13/36 20130101 |
Class at
Publication: |
348/349 ;
382/195; 348/E05.045 |
International
Class: |
G06K 9/46 20060101
G06K009/46; H04N 5/232 20060101 H04N005/232 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2006 |
JP |
2006-238587 |
Claims
1. A camera comprising: an image sensor imaging an object image; a
face detecting section detecting a face area in a shooting screen
based on an output of the image sensor; a focus detecting section
having a plurality of optional areas in the shooting screen and
calculating a defocus amount from a relative interval of a pair of
images based on an optical flux passed through a shooting lens in
each of the optional areas; a first focus controlling section
specifying a focus detecting area from the optional areas based on
an output of the face detecting section and performing a focus
operation of the shooting lens based on the defocus amount of the
focus detecting area; a second focus controlling section
calculating a focus evaluation value in the face area based on an
output of the image sensor, searching a lens position where the
focus evaluation value becomes a maximum value, and performing a
focus operation; and a control section causing at least one of the
first focus controlling section and the second focus controlling
section to perform a focus operation.
2. The camera according to claim 1, wherein when the face area is
detected within a calculable range of the defocus amount, the
control section causes the first focus controlling section to
perform a focus operation, and thereafter further causes the second
focus controlling section to perform a focus operation.
3. The camera according to claim 1, wherein when the face area is
detected outside a calculable range of the defocus amount, the
control section causes the second focus controlling section to
perform a focus operation.
4. The camera according to claim 1, further comprising an alarm
section alarming a user when the face area is detected outside a
calculable range of the defocus amount.
5. The camera according to claim 1, further comprising an object
distance calculating section calculating a first object distance
based on the defocus amount of the focus detecting area and
calculating a second object distance based on a size of the face
area, when the face area is detected within a calculable range of
the defocus amount, wherein the control section determines
necessity of a focus operation of each of the first focus
controlling section and the second focus controlling section based
on a difference between the first object distance and the second
object distance.
6. The camera according to claim 2, wherein when there is a
plurality of the optional areas corresponding to the face area, the
first focus controlling section specifies one of the optional areas
closest to a center of the face area as the focus detecting
area.
7. The camera according to claim 2, wherein when there is a
plurality of the optional areas corresponding to the face area, the
first focus controlling section specifies one of the optional areas
corresponding to positions of eyes of the face area as the focus
detecting area.
8. The camera according to claim 7, wherein when there is a
plurality of the optional areas corresponding to positions of eyes
of the face area, the first focus controlling section specifies one
of the optional areas closest to a center of the shooting screen as
the focus detecting area.
9. The camera according to claim 7, wherein when there is a
plurality of the optional areas corresponding to positions of eyes
of the face area, the first focus controlling section specifies one
of the optional areas where the eyes of the face area are on a side
closest to the camera as the focus detecting area.
10. The camera according to claim 2, further comprising: a memory
recording registration data indicating feature points of a face to
be a recognized target; and a face recognizing section extracting
feature points of a face of an object from the face area, and
determining whether or not the face area is the recognized target
based on data of the feature points extracted from the face area
and the registration data, wherein when detected number of the face
area is two or more, the first focus controlling section specifies
the focus detecting area from one of the optional areas
corresponding to the face of the recognized target.
11. The camera according to claim 2, wherein when detected number
of the face area is two or more, the first focus controlling
section specifies the focus detecting area from one of the optional
areas corresponding to a face on a side closest to the camera.
12. The camera according to claim 11, wherein the first focus
controlling section specifies the focus detecting area from a face
of which portions of eyes of the face area are on the side closest
to the camera.
13. The camera according to claim 1, further comprising: a memory
recording registration data indicating feature points of a face to
be a recognized target; and a face recognizing section extracting
feature points of a face of an object from the face area, and
determining whether or not the face area is the recognized target
based on data of the feature points extracted from the face area
and the registration data, wherein when the face area of the
recognized target is detected outside a calculable range of the
defocus amount, the control section causes the second focus
controlling section to perform a focus operation based on the face
area of the recognized target.
14. The camera according to claim 1, further comprising: a memory
recording registration data indicating feature points of a face to
be a recognized target; a face recognizing section extracting
feature points of a face of an object from the face area, and
determining whether or not the face area is the recognized target
based on data of the feature points extracted from the face area
and the registration data; and an alarm section alarming a user
when the face area of the recognized target is detected outside a
calculable range of the defocus amount.
15. The camera according to claim 1, wherein the control section
adjusts a depth of field based on the defocus amount obtained from
each of a plurality of the optional areas located in the face
area.
16. The camera according to claim 1, wherein when a size of the
face area is equal to or larger than a threshold, the control
section causes the first focus controlling section to perform a
focus operation and thereafter further causes the second focus
controlling section to perform a focus operation, and when the size
of the face area is smaller than the threshold, the control section
causes the first focus controlling section to perform a focus
operation.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application of
International Application No. PCT/JP2007/000921, filed Aug. 28,
2007, designating the U.S., in which the International Application
claims a priority date of Sep. 4, 2006, based on prior filed
Japanese Patent Application No. 2006-238587, the entire contents of
which are incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates to a camera which performs
focus control based on a result of face detection.
[0004] 2. Description of the Related Art
[0005] Conventionally, as shown in Japanese Unexamined Patent
Application Publication No. 2005-86682 for example, cameras
performing automatic focus control (AF) by detecting a face of an
object within a shooting screen are publicly known. Particularly,
in recent years, it is considered to realize AF with face detection
in a single lens reflex type camera.
[0006] Here, when performing AF of face detection in a single lens
reflex type camera, the following problems are pointed out. The
majority of single lens reflex type cameras are models employing a
focus detecting device of a phase difference detection method for
performing high-speed AF. However, the focus detecting device of
the phase difference detection method has a difficulty in focus
detection on the entire region of a shooting screen, and has a
device structure that is not suitable for face detection
processing.
[0007] On the other hand, for performing face detection AF, a
structure is also conceivable that performs image-plane AF by a
contrast detection method with an image sensor for performing face
detection. With contrast detection AF, it is possible to perform AF
on the entire region of the shooting screen. However, the contrast
detection AF takes time for a focus operation because it searches
for a focus position by comparison with focus evaluation values of
the previous time. Therefore, particularly for single lens reflex
type cameras, it is strongly demanded to realize face detection AF
that is highly practical. Note that Japanese Unexamined Patent
Application Publication No. 2005-86682 does not disclose any means
for solving the above-described problems.
SUMMARY
[0008] The present invention is for solving the above-described
conventional problems. An object of the present invention is to
provide a highly practical single lens reflex type camera which
realizes an optimum AF operation based on a result of face
detection.
[0009] A camera according to a first invention includes an image
sensor, a face detecting section, a focus detecting section, a
first focus controlling section, a second focus controlling
section, and a control section. The image sensor images an object
image. The face detecting section detects a face area in a shooting
screen based on an output of the image sensor. The focus detecting
section has a plurality of optional areas in the shooting screen
and calculates a defocus amount from a relative interval of a pair
of images based on an optical flux passed through a shooting lens
in each of the optional areas. The first focus controlling section
specifies a focus detecting area from the optional areas based on
an output of the face detecting section, and performs a focus
operation of the shooting lens based on the defocus amount of the
focus detecting area. The second focus controlling section
calculates a focus evaluation value in the face area based on an
output of the image sensor, searches a lens position where the
focus evaluation value becomes a maximum value, and performs a
focus operation. The control section causes at least one of the
first focus controlling section and the second focus controlling
section to perform a focus operation.
[0010] In a second invention according to the first invention, when
the face area is detected within a calculable range of the defocus
amount, the control section causes the first focus controlling
section to perform a focus operation, and thereafter further causes
the second focus controlling section to perform a focus
operation.
[0011] In a third invention according to the first invention, when
the face area is detected outside a calculable range of the defocus
amount, the control section causes the second focus controlling
section to perform a focus operation.
[0012] In a fourth invention according to the first invention, the
camera further includes an alarm section. The alarm section alarms
a user when the face area is detected outside a calculable range of
the defocus amount.
[0013] In a fifth invention according to the first invention, the
camera further includes an object distance calculating section. The
object distance calculating section calculates a first object
distance based on the defocus amount of the focus detecting area
and calculates a second object distance based on a size of the face
area, when the face area is detected within a calculable range of
the defocus amount. Then the control section determines necessity
of a focus operation of each of the first focus controlling section
and the second focus controlling section based on a difference
between the first object distance and the second object
distance.
[0014] In a sixth invention according to the second invention, when
there is a plurality of the optional areas corresponding to the
face area, the first focus controlling section specifies one of the
optional areas closest to a center of the face area as the focus
detecting area.
[0015] In a seventh invention according to the first invention,
when there is a plurality of the optional areas corresponding to
the face area, the first focus controlling section specifies one of
the optional areas corresponding to positions of eyes of the face
area as the focus detecting area.
[0016] In an eighth invention according to the seventh invention,
when there is a plurality of the optional areas corresponding to
positions of eyes of the face area, the first focus controlling
section specifies one of the optional areas closest to a center of
the shooting screen as the focus detecting area.
[0017] In a ninth invention according to the seventh invention,
when there is a plurality of the optional areas corresponding to
positions of eyes of the face area, the first focus controlling
section specifies one of the optional areas where the eyes of the
face area are on a side closest to the camera as the focus
detecting area.
[0018] In a tenth invention according to the second invention, the
camera further includes a memory and a face recognizing section.
The memory records registration data indicating feature points of a
face to be a recognized target. The face recognizing section
extracts feature points of a face of an object from the face area,
and determines whether or not the face area is the recognized
target based on data of the feature points extracted from the face
area and the registration data. Then, when detected number of the
face area is two or more, the first focus controlling section
specifies as the focus detecting area from one of the optional
areas corresponding to the face of the recognized target.
[0019] In an eleventh invention according to the second invention,
when detected number of the face area is two or more, the first
focus controlling section specifies as the focus detecting area
from one of the optional areas corresponding to a face on a side
closest to the camera.
[0020] In a twelfth invention according to the eleventh invention,
the first focus controlling section specifies the focus detecting
area from a face of which portions of eyes of the face area are on
the side closest to the camera.
[0021] In a thirteenth invention according to the first invention,
the camera further includes a memory and a face recognizing
section. The memory records registration data indicating feature
points of a face to be a recognized target. The face recognizing
section extracts feature points of a face of an object from the
face area, and determines whether or not the face area is the
recognized target based on data of the feature points extracted
from the face area and the registration data. Then, when the face
area of the recognized target is detected outside a calculable
range of the defocus amount, the control section causes the second
focus controlling section to perform a focus operation based on the
face area of the recognized target.
[0022] In a fourteenth invention according to the first invention,
the camera further includes a memory, a face recognizing section,
and an alarm section. The memory records registration data
indicating feature points of a face to be a recognized target. The
face recognizing section extracts feature points of a face of an
object from the face area, and determines whether or not the face
area is the recognized target based on data of the feature points
extracted from the face area and the registration data. The alarm
section alarms a user when the face area of the recognized target
is detected outside a calculable range of the defocus amount.
[0023] In a fifteenth invention according to the first invention,
the control section adjusts a depth of field based on the defocus
amount obtained from each of a plurality of the optional areas
located in the face area.
[0024] In a sixteenth invention according to the first invention,
when a size of the face area is equal to or larger than a
threshold, the control section causes the first focus controlling
section to perform a focus operation and thereafter further causes
the second focus controlling section to perform a focus operation.
Further, when the size of the face area is smaller than the
threshold, the control section causes the first focus controlling
section to perform a focus operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a block diagram showing a structure of an
electronic camera of a first embodiment.
[0026] FIG. 2 is a schematic diagram showing a photographing
mechanism of the electronic camera of the first embodiment.
[0027] FIG. 3 is a diagram showing an arrangement of optional areas
in a shooting screen.
[0028] FIG. 4 is a perspective view showing an overview of an
optical system of a focus detecting section in the first
embodiment.
[0029] FIG. 5 is a flowchart showing an example of a shooting
operation of the electronic camera in the first embodiment.
[0030] FIG. 6 is a diagram showing an example of a focus detection
range of the focus detecting section in the shooting screen.
[0031] FIG. 7 is a flowchart of a subroutine in S105 of FIG. 5.
[0032] FIG. 8 is a flowchart showing a shooting operation example
of an electronic camera in a second embodiment.
[0033] FIG. 9 is a flowchart showing a shooting operation example
of an electronic camera in a third embodiment.
[0034] FIG. 10 is a flowchart showing a shooting operation example
of an electronic camera in a fourth embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Description of a First Embodiment
[0035] FIG. 1 is a block diagram showing a structure of an
electronic camera of a first embodiment. FIG. 2 is a schematic
diagram showing a photographing mechanism of the electronic camera
of the first embodiment.
[0036] First, the photographing mechanism of the electronic camera
will be described with reference to FIG. 2. The electronic camera
of the first embodiment has a camera body 11 and a lens unit 12
housing a photographing optical system.
[0037] Here, the camera body 11 and the lens unit 12 are provided
respectively with a pair of mounts (not shown) in a male-female
relationship. The lens unit 12 is coupled replaceably to the camera
body 11 by coupling the above mounts by a bayonet mechanism or the
like. Further, the mounts are each provided with an electrical
contact. When the camera body 11 and the lens unit 12 are coupled,
an electrical connection is established between them by the contact
between the electrical contacts.
[0038] The lens unit 12 has a focusing lens 13 for focus position
adjustment and a diaphragm 14. The focusing lens 13 is structured
movably in an optical axis direction by a not-shown motor. The
diaphragm 14 adjusts an incident light amount in the camera body 11
by opening/closing diaphragm blades.
[0039] The camera body 11 has a main mirror 15, a mechanical
shutter 16, a first image sensor 17, a sub-mirror 18, a focus
detecting section 19, and a finder optical system (20 to 25). The
main mirror 15, the mechanical shutter 16, and the first image
sensor 17 are arranged along the optical axis of the photographing
optical system. The sub-mirror 18 is arranged behind the main
mirror 15. Further, the finder optical system is arranged in an
upper region of the camera body 11. Moreover, the focus detecting
section 19 is arranged in a lower region of the camera body 11.
[0040] The main mirror 15 is pivotally supported by a not-shown
pivot shaft, and is capable of switching between an observation
state and a retracted state. The main mirror 15 in the observation
state is arranged obliquely in front of the mechanical shutter 16
and the first image sensor 17. The main mirror 15 in the
observation state reflects upward an optical flux passed through
the photographing optical system and guides it to the finder
optical system. Further, a center portion of the main mirror 15 is
a half mirror. Part of the optical flux transmitted through the
main mirror 15 is then bent downward by the sub-mirror 18 and is
guided to the focus detecting section 19. On the other hand, the
main mirror 15 in the retracted state is flipped upward together
with the sub-mirror 18 and is at a position deviated from a
photographing optical path. When the main mirror 15 is in the
retracted state, the optical flux passed through the photographing
optical system is guided to the mechanical shutter 16 and the first
image sensor 17.
[0041] The finder optical system has a diffusion screen (focus
plate) 20, a condenser lens 21, a pentagonal prism 22, a beam
splitter 23, a second image sensor 24, and an eyepiece lens 25. The
diffusion screen 20 is located above the main mirror 15, and images
once the optical flux reflected by the main mirror 15 in the
observation state. The optical flux imaged on the diffusion screen
20 passes through the condenser lens 21 and the pentagonal prism 22
and is guided to the beam splitter 23 via an exit surface at a
90.degree. angle with an incident surface of the pentagonal prism
22. The beam splitter 23 branches the incident optical flux in two
directions. One optical flux passing through the beam splitter 23
is guided to the second image sensor 24 via a secondary imaging
lens (not shown). Further, the other optical flux passing through
the beam splitter 23 reaches the user's eye via the eyepiece lens
25.
[0042] Next, a circuit structure of the electronic camera will be
described with reference to FIG. 1. The camera body 11 has the
focus detecting section 19, a recording-purpose imaging section 31,
an analyzing-purpose imaging section 32, a first memory 33, a
recording I/F 34, a display I/F 36, a monitor 37, an in-finder
display panel 37a, an operation unit 38, a CPU 39, a second memory
40, and a system bus 41. Here, the recording-purpose imaging
section 31, the first memory 33, the recording I/F 34, the display
I/F 36, and the CPU 39 are coupled via the system bus 41. Note that
illustration of input/output of the CPU 39 from/to the lens unit 12
side is omitted in FIG. 1.
[0043] The focus detecting section 19 detects a focusing state in
optional areas set in advance in a shooting screen. The focus
detecting section 19 of the first embodiment has 11 optional areas
in the shooting screen. In FIG. 3, an arrangement of optional areas
(A1 to A11) within the shooting screen is shown. In a center
portion of the shooting screen, optional areas A2 to A10 are
arranged in a 3.times.3 lattice form. Further, on left and right
sides in the shooting screen, optional areas A1 and A11 are
arranged across the aforementioned optional areas arranged in a
lattice form.
[0044] Further, FIG. 4 shows an overview of the optical system of
the focus detecting section 19 of the first embodiment. This focus
detecting section 19 includes five groups of focus detecting
optical systems. The left and right focus detecting optical systems
in FIG. 4 correspond to the optional areas A1 and A11,
respectively. Then three focus detecting optical systems in the
middle correspond to the optional areas A2 to A10, respectively.
Each of the focus detecting optical systems has a visual field mask
19a, a condenser lens 19b, an aperture mask 19c, a separator lens
19d, and a line sensor 19e. In FIG. 4, a king-shaped (back-to-back
E shaped) opening is formed in the visual field mask 19a of each of
the three focus detecting optical systems in the middle. Further, a
longitudinally shaped opening extending in a vertical direction is
formed in the visual field mask 19a of each of the focus detecting
optical systems on the left and right sides. Then the respective
focus detecting optical systems divide an optical flux from an
object by the condenser lenses 19b and the separator lenses 19d,
and detect an image displacement amount of the object from an
interval of two images by the line sensors 19e corresponding to the
respective optional areas.
[0045] The recording-purpose imaging section 31 has the first image
sensor 17, a first analog processing section 31a, and a first
digital processing section 31b.
[0046] The first image sensor 17 is a sensor for generating a
recording-purpose shot image. This first image sensor 17
photoelectrically converts an object image that is passed through
the photographing optical system and imaged when the shutter is
released so as to generate an analog signal of a shot image. An
output signal of the first image sensor 17 is input to the first
analog processing section 31a.
[0047] The first analog processing section 31a is an analog
front-end circuit having a CDS circuit, a gain circuit, an A/D
converter circuit, and so on. The CDS circuit reduces noise
components in an output of the first image sensor 17 by correlated
double sampling. The gain circuit amplifies the gain of an input
signal and outputs it. This gain circuit is capable of adjusting
photographing sensitivity corresponding to the ISO sensitivity. The
A/D converter circuit performs A/D conversion of an output signal
of the first image sensor 17. Note that illustration of the
respective circuits of the first analog processing section 31a is
omitted in FIG. 1.
[0048] The first digital processing section 31b performs various
types of image processing (defective pixel correction, color
interpolation, gradation conversion processing, white balance
adjustment, edge enhancement, and so on) on an output signal of the
first analog processing section 31a so as to generate data of a
shot image. Further, the first digital processing section 31b also
performs companding processing of data of a shot image, or the
like. This first digital processing section 31b is coupled to the
system bus 41.
[0049] The analyzing-purpose imaging section 32 has the second
image sensor 24, a second analog processing section 32a, and a
second digital processing section 32b. Note that the structure of
the analyzing-purpose imaging section 32 substantially corresponds
to the structure of the recording-purpose imaging section 31, and
thus part of description regarding overlapping portions of the both
is omitted.
[0050] The second image sensor 24 is a sensor for analyzing the
status of an object in the shooting screen when waiting for
shooting. The second image sensor 24 photoelectrically converts an
object image, which is passed through the finder optical system and
imaged, at every predetermined interval so as to generate an analog
signal of a through image. Data of this through image is used for
automatic exposure (AE) calculation and face detection processing,
which will be described later. An output signal of the second image
sensor 24 is input to the second analog processing section 32a.
[0051] The second analog processing section 32a is an analog
front-end circuit having a CDS circuit, a gain circuit, an A/D
conversion circuit, and so on. The second digital processing
section 32b performs color interpolation processing or the like of
the through image. Note that the data of the through image output
from the second digital processing section 32b is input to the CPU
39.
[0052] The first memory 33 is a buffer memory for temporarily
recording data of a shot image in a preceding or succeeding process
or the like of image processing by the first digital processing
section 31b.
[0053] In the recording I/F 34, a connector for coupling a
recording medium 35 is formed. Then the recording I/F 34 performs
writing/reading of data of a shot image from/to the recording
medium 35 coupled to the connector. The aforementioned recording
medium 35 is formed of a memory card or the like including a hard
disk or a semiconductor memory. Note that in FIG. 1 a memory card
is shown as an example of the recording medium 35.
[0054] The display I/F 36 controls display of the monitor 37 based
on an instruction from the CPU 39. The monitor 37 displays various
images in response to instructions of the CPU 39 and the display
I/F 36. The monitor 37 in the first embodiment is formed of a
liquid crystal display monitor. On the monitor 37, a reproduced
image of a shot image, a menu screen capable of inputting in a GUI
(graphical user interface) form, and/or the like can be displayed.
Further, on the monitor 37, it is also possible to display by
moving image the state of a field when on standby for shooting
based on the through image of the analyzing-purpose imaging section
32 (note that illustration of the above images is omitted).
[0055] The in-finder display panel 37a is a panel for presenting
information of the electronic camera (shooting condition and
various alarm displays) to the user looking through the finder
optical system. This in-finder display panel 37a displays the above
information in a periphery of a finder image corresponding to the
shooting screen by switching on and off of lights of plural display
segments. In addition, control of display of the in-finder display
panel 37a is performed by the CPU 39.
[0056] The operation unit 38 has a release button, an operating
button, and so on. The release button of the operation unit 38
accepts from the user an instruction input of starting an exposure
operation. The operating button of the operation unit 38 accepts
from the user an input on the aforementioned menu screen or the
like, an input of switching a shooting mode of the electronic
camera, or the like.
[0057] The CPU 39 controls operations of respective parts of the
electronic camera, and performs various calculations needed for
photographing. For example, the CPU 39 drives the main mirror 15,
the mechanical shutter 16, and so on when shooting. Further, the
CPU 39 controls operations of the focusing lens 13 and the
diaphragm 14 of the lens unit 12 via the mounts.
[0058] Further, the CPU 39 functions as an AE calculating section
39a, a first AF calculating section 39b, a face detecting section
39c, a second AF calculating section 39d, and a face recognizing
section 39e by a program stored in a not-shown ROM.
[0059] The AE calculating section 39a performs a publicly known AE
calculation based on an output of the analyzing-purpose imaging
section 32 and decides shooting conditions (exposure time, aperture
value, photographing sensitivity) for shooting.
[0060] The first AF calculating section 39b selects a focus
detecting area from the optional areas of the focus detecting
section 19. The first AF calculating section 39b then calculates a
defocus amount (displacement amount and displacement direction from
the focus position) of the focus lens based on an output of the
focus detecting area in the focus detecting section 19. Further,
the first AF calculating section 39b selects the focus detecting
area based on a result of face detection processing by the face
detecting section 39c. Further, the first AF calculating section
39b is also capable of obtaining from the lens driving unit 12 the
position of the focus lens when focusing, and calculating an object
distance in each of the optional areas.
[0061] The face detecting section 39c detects a face area of an
object, the size of a face, and so on from the data of the through
image. For example, the face detecting section 39c extracts a face
area by extraction processing of feature points of a face, which is
described in Japanese Unexamined Patent Application Publication No.
2001-16573 or the like. Further, examples of the above-described
feature points include end points of eyebrows, eyes, a nose, and
lips, edges points of a face, a vertex point of a head, a lower end
point of a chin, and the like.
[0062] The second AF calculating section 39d performs a publicly
known AF calculation by a contrast detection method based on the
data of the through image. That is, the second AF calculating
section 39d integrates the absolute value of a high frequency
component of the through image to generate a focus evaluation value
related to a predetermined object image. Further, the second AF
calculating section 39d compares focus evaluation values before and
after moving the focusing lens 13 to search lens positions where
the focus evaluation values become maximum values, and performs a
focus operation. The second AF calculating section 39d is capable,
too, of performing an object distance based on the position of the
focus lens when focusing.
[0063] The face recognizing section 39e generates face recognizing
data based on feature points detected by the face detecting section
39c. For example, the face recognizing section 39e generates face
recognizing data of a registered person as a recognized target from
positions of detected feature points of a face, sizes of face parts
obtained from the feature points, relative distances between the
feature points, and so on.
[0064] Further, the face recognizing section 39e performs face
recognition processing to determine whether or not the face of a
person in the shooting screen is the face of a person of the face
recognizing data. Specifically, based on detected feature points of
a face, the face recognizing section 39e first calculates positions
of feature points of the face of a photographed person, sizes of
face parts, relative distances of feature points, and so on. Next,
the face recognizing section 39e compares the above calculation
results and the face recognizing data, and obtains the degree of
similarity between the face of the person of the face recognizing
data and the face of the photographed person. The face recognizing
section 39e then determines that the photographed person matches
with the person of the face recognizing data when the degree of
similarity exceeds a threshold value.
[0065] The second memory 40 is coupled to the CPU 39. In the second
memory 40, the face recognizing data generated in the face
recognizing section 39e is recorded. In this second memory 40, a
group folder can be generated for each registered person
(registered person), and face recognizing data can be grouped for
each registered person with the group folder. For example, in the
group folder, plural sets of face recognizing data can be recorded
which are different in face direction, shooting condition, and so
on for the same registered person.
[0066] Next, with reference to a flow chart of FIG. 5, an example
of shooting operations of the electronic camera of the first
embodiment will be described. Note that the following description
is given under the assumption that the face detecting function of
the electronic camera is set to ON in advance, and the user
performs framing with the finder optical system.
[0067] Step 101: when the operation unit 38 accepts a start
operation of a shooting mode from the user, the CPU 39 instructs
the analyzing-purpose imaging section 32 to start obtaining a
through image. The CPU 39 drives the second image sensor 24 at
every predetermined interval to obtain the through image
sequentially. Incidentally, the main mirror 15 is at the position
of the observation state in the stage of S101.
[0068] Step 102: the CPU 39 determines whether the release button
is half pressed or not. When the release button is half pressed
(YES side), the process proceeds to S103. On the other hand, when
there is no input on the release button (NO side), the CPU 39 waits
for half pressing of the release button.
[0069] Step 103: the face detecting section 39c of the CPU 39
performs face detection processing on data of the through image to
detect a face area in the shooting screen. Incidentally, in the
first embodiment, the face detecting section 39c performs the face
detection processing targeted at the entire range of the shooting
screen.
[0070] Step 104: the CPU 39 determines whether a face area is
detected or not by the face detection processing in S103. When this
condition is met (YES side), the process proceeds to S105. On the
other hand, when this condition is not met (NO side), the process
proceeds to S112.
[0071] Step S105: the face detecting section 39c of the CPU 39
specifies a face area of a main object based on the face detection
result of S103. Details of an algorithm for selecting the main
object in this S105 will be described later.
[0072] Step 106: the CPU 39 determines whether or not the face area
of the main object set in S105 overlaps with any one of the
optional areas. In addition, an example of a focus detection range
of the focus detecting section 19 in the first embodiment is shown
schematically in FIG. 6. As a matter of course, when the object
overlaps with no optional area, focus detection in the focus
detecting section 19 cannot be performed. When this condition is
met (YES side), the process proceeds to S107. On the other hand,
when this condition is not met (NO side), the process proceeds to
S111.
[0073] Step S107: the first AF calculating section 39b of the CPU
39 obtains a defocus amount of each of the optional areas from the
focus detecting section 19.
[0074] Step 108: the first AF calculating section 39b of the CPU 39
specifies the focus detecting area from the optional area
corresponding to the face area (S105) of the main object. Here,
when there is one optional area corresponding to the face area of
the main object, the first AF calculating section 39b specifies
this optional area as the focus detecting area. On the other hand,
when there are plural optional areas corresponding to the face area
of the main object, the first AF calculating section 39b selects
the optional area to be the focus detecting area by the following
method (1) or (2).
[0075] (1) The first AF calculating section 39b specifies the
optional area closest to the center of a face area of the selected
target as the focus detecting area. This center of the face area
changes depending on the direction of the face. For example, on a
front side of the face, the vicinity of the nose is the center of
the face, and on a side of the face, the vicinity of the ear is the
center of the face.
[0076] Specifically, the first AF calculating section 39b obtains
the center of a face with reference to the edge of the face or a
fresh color region that can be assumed as a face, and specifies the
focus detecting area. Alternatively, the first AF calculating
section 39b may obtain the center of a face from a positional
relationship of the parts (eyes, nose, mouth, and so on) forming
the face. In this way, the first AF calculating section 39b can
specify the focus detecting area relatively easily.
[0077] (2) The first AF calculating section 39b specifies the
optional area corresponding to the positions of eyes in a face area
of the selected target as the focus detecting area. This is because
it is preferable to focus on the eyes when photographing a person.
Specifically, the first AF calculating section 39b obtains
positions of eyes based on feature points of the face area and
specifies the focus detecting area.
[0078] Here, when there are two or more optional areas
corresponding to the positions of eyes in the face area, the first
AF calculating section 39b further specifies the focus detecting
area by either of the following methods.
[0079] First, the first AF calculating section 39b specifies an
optional area closer to the center of the shooting screen as the
focus detecting area. In this way, the electronic camera can
realize AF in line with the user's general photographing
intention.
[0080] Secondly, the first AF calculating section 39b compares
outputs of the above optional areas corresponding to eyes and
specifies the optional area located where the object is on the side
closest to the camera as the focus detecting area. In this way, the
electronic camera can realize AF that is more suitable, for
example, in a scene of photographing a person obliquely facing the
camera.
[0081] Step 109: the first AF calculating section 39b performs AF
based on the defocus amount of the focus detecting area specified
in S108. Incidentally, the AF of the first AF calculating section
39b in S109 is performed for narrowing down the search range of the
AF by the second AF calculating section 39d.
[0082] Step 110: the second AF calculating section 39d performs the
contrast detection AF with reference to the focus detecting area of
S108. Thereafter, the process proceeds to S113.
[0083] Step 111: the second AF calculating section 39d performs the
contrast detection AF with reference to the position of the face
area (S105) of the main object. Note that in this S111, the AF is
performed for a face located outside the range overlapping with the
above optional areas of the focus detecting section 19. Thereafter,
the process proceeds to S113.
[0084] Step 112: in this flow, the CPU 39 performs AF with an
object other than a face being the main object by an algorithm for
normal shooting. For example, the CPU 39 selects the focus
detecting area from the center or the side closest to the camera by
priority, and performs AF by the first AF calculating section 39b.
The CPU 39 may of course perform hybrid AF by operating both the
first AF calculating section 39b and the second AF calculating
section 39d.
[0085] Step 113: the AE calculating section 39a of the CPU 39
performs an AE calculation based on the through image to adjust the
shooting condition.
[0086] Here, when the face area is detected in S103, it is
preferable that the AE calculating section 39a adjusts the depth of
field by controlling an aperture value based on an object
distance.
[0087] Specifically, the AE calculating section 39a obtains the
object distance of the face area from the first AF calculating
section 39b or the second AF calculating section 39d. Then the AE
calculating section 39a increases the aperture value based on the
object distance to make the depth of field deeper. This allows to
create a state of being in focus on the entire face area. Further,
in a scene of photographing plural persons, it becomes possible to
focus on all the persons.
[0088] Step 114: the CPU 39 determines whether the release button
is fully pressed or not.
[0089] When the release button is fully pressed (YES side), the
process proceeds to S115. On the other hand, when there is no input
on the release button (NO side), the CPU 39 waits for full pressing
of the release button.
[0090] Step 115: the CPU 39 retracts the main mirror 15 from the
photographing optical path and drives the first image sensor 17 to
shoot an object image.
[0091] Step 116: the CPU 39 instructs the recording-purpose imaging
section 31 to generate data of the shot image. Then the data of the
shot image is recorded in the recording medium 35 finally. Thus, a
series of shooting operations is completed. Incidentally, when
shooting is continued, the CPU 39 returns to S102 and repeats the
above operations.
[0092] Next, an operation of selecting a main object in S105 of
FIG. 5 will be described in detail with reference to a flowchart of
FIG. 7.
[0093] Step 201: the CPU 39 determines whether or not one face area
is detected by the face detection processing of S103. When one face
area is detected (YES side), the process proceeds to S202. On the
other hand, when plural face areas are detected (NO side), the
process proceeds to S203.
[0094] Step 202: the CPU 39 specifies the detected face area as the
main object.
[0095] Step 203: the face recognizing section 39d of the CPU 39
performs face recognition processing for detecting a face of a
registered person to be a recognized target from the aforementioned
face areas based on the data of feature points obtained in the face
detection processing of S103 and the face recognizing data in the
second memory 40.
[0096] Step 204: the CPU 39 determines whether the face of the
registered person is detected or not by the face recognition
processing of S203. When the face of the registered person is
detected (YES side), the process proceeds to S205. On the other
hand, when the face area is not detected (NO side), the process
proceeds to S206.
[0097] Step 205: the CPU 39 specifies the face area of the
registered person as the main object. Further, when plural faces of
registered persons are detected in S203, the CPU 39 specifies a
face among the faces of the registered persons that is close to the
center of the shooting screen or a face on the side closest to the
camera as the main object.
[0098] Here, when the face on the side closest to the camera is
specified as the main object, the CPU 39 specifies, as a first
method, the face that has the largest area and can be considered as
being located on the side closest to the camera as the main object.
Alternatively, as a second method, the CPU 39 may obtain the object
distance from the first AF calculating section 39b and specify the
face on the side closest to the camera as the main object. In
addition, in the above second method, it is preferable that the CPU
39 determines the face on the side closest to the camera based on
the positions of eyes in the face area.
[0099] Step 206: the CPU 39 determines whether or not there is a
face area overlapping with the optional areas of the focus
detecting section 19 in the shooting screen. When this condition is
met (YES side), the process proceeds to S207. On the other hand,
when this condition is not met (NO side), the process proceeds to
S208.
[0100] Step 207: the CPU 39 specifies the main object from the face
area overlapping with the optional areas of the focus detecting
section 19. Further, when there are plural face areas satisfying
the above condition, the CPU 39 specifies the face area on the side
closest to the camera as the main object. The method for selecting
the face on the side closest to the camera is the same as in S205,
and thus overlapping description is omitted.
[0101] Step 208: the CPU 39 specifies the face area on the side
closest to the camera from the plural detected face areas as the
main object. The method for selecting the face on the side closest
to the camera is the same as in S205, and thus overlapping
description is omitted. In addition, this S208 results in that the
face area of the main object is selected from the outside of the
range overlapping with the optional areas of the focus detecting
section 19.
[0102] Hereinafter, effects of the electronic camera of the first
embodiment will be described.
[0103] The electronic camera of the first embodiment performs the
hybrid AF when the face of a main object is detected in the range
overlapping with the optional areas of the focus detecting section
19. That is, in the above case, the electronic camera limits the
search range by phase difference detection AF, and thereafter
performs fine adjustment of the focus position by the contrast
detection AF (S106 to S110). Therefore, the electronic camera of
the first embodiment can realize AF that is targeted at the face of
an object overlapping with the optional areas of the focus
detecting section 19, and in which the time required until focusing
is reduced while ensuring high focusing accuracy.
[0104] Moreover, the electronic camera of the first embodiment
performs the contrast detection AF based on an output of the
analyzing-purpose imaging section 32 (S106, S111) when the face of
a main object is detected in the range not overlapping with the
optional areas of the focus detecting section 19. Therefore, with
the electronic camera of the first embodiment, AF can be performed
also for a face detected outside the range overlapping with the
optional areas of the focus detecting section 19, and thus focusing
in line with the user's intention can be performed flexibly.
Description of a Second Embodiment
[0105] FIG. 8 is a flowchart showing a shooting operation example
of an electronic camera according to a second embodiment. Here, the
basic structure of the electronic camera in the embodiment below is
common to that of the first embodiment, and hence overlapping
description is omitted.
[0106] The second embodiment is a modification example of the first
embodiment, and S301 to S310 in FIG. 8 correspond respectively to
S101 to S110 of the first embodiment. Further, S314 to S318 in FIG.
8 correspond respectively to S112 to S116 of the first embodiment.
Accordingly, overlapping description of the above steps shown in
FIG. 8 is omitted.
[0107] Step 311: the CPU 39 instructs the in-finder display panel
37a to perform alarm display. The in-finder display panel 37a
lights a predetermined display segment to perform alarm display
indicating that the face area of the main object is located outside
the range overlapping with the optional areas of the focus
detecting section 19.
[0108] Step 312: the CPU 39 determines whether half pressing of the
release button is released or not. When the half pressing of the
release button is released (YES side), it returns to S302 and the
CPU 39 waits for a half press operation. On the other hand, when
the half pressing of the release button is continued (NO side), the
process proceeds to S313.
[0109] Step 313: the CPU 39 specifies again as the main object and
performs AF. Thereafter, the process proceeds to S315
(corresponding to S113 of the first embodiment).
[0110] Here, in S313, the CPU 39 specifies the object overlapping
with the optional areas of the focus detecting section 19 as the
main object. For example, the CPU 39 specifies again an object
other than a face as the main object by the algorithm for normal
shooting. Alternatively, when a face located outside the range
overlapping with the above optional areas is specified as the main
object by face recognition processing (as in S205 shown in FIG. 7),
the CPU 39 specifies again the main object from the face of a
person other than the registered person. Incidentally, in S313, the
CPU 39 performs AF by the first AF calculating section 39b. The CPU
39 may of course perform hybrid AF by operating both the first AF
calculating section 39b and the second AF calculating section
39d.
[0111] The electronic camera of the second embodiment performs the
warning display when the face of the main object is located outside
the range overlapping with the optional areas of the focus
detecting section 19, specifies the main object again, and performs
AF (S311 to S313). Therefore, with the electronic camera of the
second embodiment, the user can easily comprehend a situation that
the hybrid AF cannot be performed by alarm display.
Description of a Third Embodiment
[0112] FIG. 9 is a flowchart showing a shooting operation example
of an electronic camera according to a third embodiment.
[0113] The third embodiment is a modification example of the first
embodiment, and S401 to S408 in FIG. 9 correspond respectively to
S101 to S108 of the first embodiment. Further, S414 to S419 in FIG.
9 correspond respectively to S111 to S116 of the first embodiment.
Accordingly, overlapping description of the above steps shown in
FIG. 9 is omitted.
[0114] Step 409: the first AF calculating section 39b of the CPU 39
calculates a first object distance from a defocus amount of the
focus detecting area.
[0115] Step 410: CPU 39 calculates a second object distance from
the size of a face area of the main object. For example, based on a
table or a calculation formula representing the correspondence
between the size of a face area and an object distance, the CPU 39
can obtain the second object distance from the size of the face
area.
[0116] Step 411: the CPU 39 determines whether or not a difference
between the first object distance (S409) and the second object
distance (S410) is in the range of tolerated error. When this
condition is met (YES side), the process proceeds to S412. On the
other hand, when this condition is not met (NO side), the process
proceeds to S413.
[0117] Step 412: the first AF calculating section 39b performs AF
based on the defocus amount of the focus detecting area specified
in S408. Thereafter, the process proceeds to S416 (corresponding to
S113 of the first embodiment).
[0118] Step 413: the second AF calculating section 39d performs the
contrast detection AF based on the focus detecting area of S408.
Thereafter, the process proceeds to S416 (corresponding to S113 of
the first embodiment).
[0119] The electronic camera of the third embodiment performs the
phase difference detection AF when the difference between the first
and second object distances is small, and meanwhile performs the
contrast detection AF when the difference between the first and
second object distances is large. Therefore, the electronic camera
of the third embodiment is capable of selecting and using AF by
face detection more appropriately for each scene of shooting,
depending on reliability of object distances by the focus detecting
section 19.
Description of a Fourth Embodiment
[0120] FIG. 10 is a flowchart showing a shooting operation example
of an electronic camera according to a fourth embodiment.
[0121] The fourth embodiment is a modification example of the first
embodiment, and S501 to S509 in FIG. 10 correspond respectively to
S101 to S109 of the first embodiment. Further, S511 to S517 in FIG.
10 correspond respectively to S110 to S116 of the first embodiment.
Accordingly, overlapping description of the above steps shown in
FIG. 10 is omitted.
[0122] Step 510: the CPU 39 determines whether the size of a face
area of the main object is equal to or larger than a threshold
value or not. When the size of the face area is equal to or larger
than the threshold value (YES side), the process proceeds to S511.
In this flow, after the phase difference detection AF by the first
AF calculating section 39b is performed, the contrast detection AF
is further performed by the second AF calculating section 39d
(S511). On the other hand, when the size of the face area is
smaller than the threshold value (NO side), the process proceeds to
S514. In this flow, after the phase difference detection AF by the
first AF calculating section 39b is performed, the process proceeds
without performing the contrast detection AF.
[0123] The electronic camera of the fourth embodiment performs the
hybrid AF when the size of the face area of the main object is
equal to or larger than the threshold value. Accordingly, focusing
accuracy on the face of the main object can be improved more, for
example, in a scene in which it is desired to shoot the face of the
object large, such as in portrait shooting or close-up shooting
where a person is the main object.
[0124] On the other hand, when the face of the main object overlaps
with the optional areas but the size of the face area is smaller
than the threshold value, the electronic camera only performs the
phase difference detection AF. Thus, in a scene where appearance of
the face of the main object is not so important, as in shooting
scenery for example, AF can be performed quickly.
Supplementary Items of the Embodiments
[0125] (1) In the above embodiments, examples of a digital camera
of single lens reflex type are described, but the present invention
is applicable to film cameras of single lens reflex type.
[0126] (2) In the above embodiments, an example of performing face
detection processing in response to a half pressing operation of
the release button is described, but it may be arranged that the
CPU performs the face detection processing from a through image at
constant intervals.
[0127] (3) In the above embodiments, an example of performing
framing with the finder optical system is described, but it may be
arranged that the framing is performed by displaying a moving image
based on the through image on the monitor.
[0128] (4) In the above first and second embodiments, it may be
arranged that when the face area of the main object is overlapping
with any one of the optional areas (YES sides in S106, S306), the
CPU 39 performs AF by a defocus amount of the focus detecting
section 19, and the contrast detection AF is omitted.
[0129] (5) In the first embodiment, it may be arranged that when
plural faces are detected and plural optional areas correspond to
the face area of the main object (S108), the CPU 39 simplifies
specifying of the focus detecting area to alleviate the calculation
load. For example, it may be arranged that the CPU 39 mechanically
specifies an optional area closer to the center of the shooting
screen as the focus detecting area, among the optional areas
corresponding to the face area of the main object.
[0130] (6) In the second embodiment, it may be arranged that when
the face of the main object is located outside the range
overlapping with the optional areas of the focus detecting section
19, the CPU 39 does not perform AF after performing alarm display
in S311.
[0131] (7) In the second embodiment, it may be arranged that the
alarm display in S311 is performed not in the in-finder display
panel 37a. For example, it may be arranged that the CPU 39 performs
the alarm display on a display panel (not shown) arranged on a back
face or upper face of the digital camera or on the monitor 37.
Further, it may be arranged that alarming the user is performed by
sound via a buzzer (not shown) for example.
[0132] (8) In the third embodiment, it may be arranged that when a
difference between the first and second object distances is within
the range of tolerable error (YES side in S411), the CPU 39
performs the hybrid AF. Further, it may be arranged that when a
difference between the first and second object distances is out of
the range of tolerable error (NO side in S411), the CPU 39
alternatively performs AF based on the second object distance.
[0133] (9) In the above embodiments, examples in which the image
sensor (24) dedicated to face detection is provided are described,
but it may be arranged that the face detection is performed by a
photometric sensor. Further, it may be arranged that the face
detection is performed by the image sensor (17) which images a
recording-purpose image.
[0134] The many features and advantages of the embodiments are
apparent from the detailed specification and, thus, it is intended
by the appended claims to cover all such features and advantages of
the embodiments that fall within the true spirit and scope thereof.
Further, since numerous modifications and changes will readily
occur to those skilled in the art, it is not desired to limit the
inventive embodiments to the exact construction and operation
illustrated and described, and accordingly all suitable
modifications and equivalents may be resorted to, falling within
the scope thereof.
* * * * *